Lead encephalopathy will be produced in the brains of rats and rhesus monkeys by the oral administration of lead. The cerebral edema accompaning this condition will be quantitatied in the rat by measurements of changes in brain water and electrolytes, as well as uptake of serum proteins. The effects of steroids and intervenous hypertonic urea on this edema will be determined. The effects of chelating agents and vitamin therapy will also be assessed. The brains of both rats and monkeys will be studied by light and electron microscopy. The results will be compared to the human condition. Chronic lesions will be produced in the monkey. These will be studied by light microscopy and correlated with the results of behavioral tests performed both during the period of intoxication and following recovery after the development of neurologic symptoms indicative of acute lead encephalopathy.